Unless otherwise indicated herein, the description provided in this section is not prior art to the claims and is not admitted to be prior art by inclusion in this section.
A typical cellular wireless network includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which user equipment devices (UEs) can operate and engage in air-interface communication with the cellular wireless network. Each base station may then be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. Within this arrangement, a UE operating in a coverage area of the cellular wireless network can engage in communication, via the cellular wireless network, with remote network entities or with other UEs operating in the cellular wireless network.
The cellular wireless network may operate in accordance with a particular air-interface protocol or “radio access technology,” examples of which include Orthogonal Frequency Division Multiple Access (OFDMA) (e.g., Long Term Evolution (LTE) or Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), and Global System for Mobile Communications (GSM), among others. Generally, the agreed air-interface protocol may define a downlink (or forward link) for carrying communications from the base stations to UEs and an uplink (or reverse link) for carrying communications from UEs to the base stations. Further, the agreed air-interface protocol may employ techniques such time-division multiplexing, frequency-division multiplexing, and/or code-division multiplexing to divide the downlink and uplink into discrete air-interface resources that are then used to carry control and/or bearer data between the base station and particular UEs.
In an OFDMA protocol such as LTE, for instance, the downlink may operate on a given carrier frequency and span a particular channel bandwidth, such as 3 MHz, 5 MHz, 10 MHz, 15 MHz, or 20 MHz. In turn, the LTE protocol may divide the downlink in both the time and frequency domains into discrete “resource blocks” that may be allocated for data transmission to UEs. For instance, in the time domain, the LTE downlink may be divided into transmission time intervals (TTIs), or sub-frames, that each have a duration of 1 millisecond (ms) and consist of two 0.5 ms timeslots. And in the frequency domain, the LTE downlink may be divided into groups of 12 sub-carriers that each have a bandwidth of 15 KHz (for a total group bandwidth of 180 kHz), with each group of sub-carriers in a given timeslot defining a different resource block. Thus, in each TTI, the LTE downlink has a finite number of resource blocks that is limited by the downlink's channel bandwidth. An OFDMA uplink may then have a similar configuration.
The LTE protocol may also define various shared downlink channels that are mapped onto the downlink's resource blocks. For instance, LTE defines a Physical Downlink Shared Channel (PDSCH), which is typically the primary downlink channel for transmitting user data to UEs. In addition, LTE defines downlink control channels that carry various types of control signaling, such as a Physical Control Format Indicator Channel (PCFICH), a Physical Hybrid ARQ Indicator Channel (PHICH), and a Physical Downlink Control Channel (PDCCH).